Neuroscience and Free Will: New study debunks Libet’s interpretation

The interconnection of neuroscience and free will has many researchers trying to make bold claims about their findings. In my last post I called Sam Harris’ conclusion that “free will is an illusion” into question. Specifically, I suggested that there were competing interpretations that could be made from the data that neuroscientist Benjamin Libet was using to debunk free will (I mentioned Al Mele’s interpretation as a counterexample to Libet’s). Finally, some neuroscientists seem to have considered Mele’s suggestion (though interestingly I read no reference to Mele) and did some science to test his alternative interpretation. It turns out that Mele was right,and in turn, that Libet was a bit hasty with his conclusion, as was Sam Harris. Click here for the New Scientist article detailing the study. So it seems that the criticisms I levied against Harris might have more sticking power as a result. Seems that Libet has been debunked and not free will. Below you’ll find some central points directly taken from the New Scientist article.
“In the early 1980s, Benjamin Libet at the University of California in San Francisco, used electroencephalography (EEG) to record the brain activity of volunteers who had been told to make a spontaneous movement. With the help of a precise timer that the volunteers were asked to read at the moment they became aware of the urge to act, Libet found there was a 200 millisecond delay, on average, between this urge and the movement itself.

But the EEG recordings also revealed a signal that appeared in the brain even earlier – 550 milliseconds, on average – before the action. Called the readiness potential, this has been interpreted as a blow to free will, as it suggests that the brain prepares to act well before we are conscious of the urge to move.

This conclusion assumes that the readiness potential is the signature of the brain planning and preparing to move. “Even people who have been critical of Libet’s work, by and large, haven’t challenged that assumption,” says Aaron Schurger of the National Institute of Health and Medical Research in Saclay, France.

One attempt to do so came in 2009. Judy Trevena and Jeff Miller of the University of Otago in Dunedin, New Zealand, asked volunteers to decide, after hearing a tone, whether or not to tap on a keyboard. The readiness potential was present regardless of their decision, suggesting that it did not represent the brain preparing to move. Exactly what it did mean, though, still wasn’t clear.

Crossing a threshold

Now, Schurger and colleagues have an explanation. They began by posing a question: how does the brain decide to make a spontaneous movement? They looked to other decision-making scenarios for clues. Previous studies have shown that when we have to make a decision based on visual input, for example, assemblies of neurons start accumulating visual evidence in favour of the various possible outcomes. A decision is triggered when the evidence favouring one particular outcome becomes strong enough to tip its associated assembly of neurons across a threshold.

Schurger’s team hypothesised that something similar happens in the brain during the Libet experiment. Volunteers, however, are specifically asked to ignore any external information before they make a spontaneous movement, so the trigger to act must be internal.

The random fluctuations of neural activity in the brain. Schurger’s team reasoned that movement is triggered when this neural noise accumulates and crosses a threshold.

To probe the idea, the team first built a computer model of such a neural accumulator. In the model, each time the neural noise crossed a threshold it signified a decision to move. They found that when they ran the model numerous times and looked at the pattern of the neural noise that led up to the decision it looked like a readiness potential.

Next, the team repeated Libet’s experiment, but this time if, while waiting to act spontaneously, the volunteers heard a click they had to act immediately. The researchers predicted that the fastest response to the click would be seen in those in whom the accumulation of neural noise had neared the threshold – something that would show up in their EEG as a readiness potential.

This is exactly what the team found. In those with slower responses to the click, the readiness potential was absent in the EEG recordings.

Spontaneous brain activity

“Libet argued that our brain has already decided to move well before we have a conscious intention to move,” says Schurger. “We argue that what looks like a pre-conscious decision process may not in fact reflect a decision at all. It only looks that way because of the nature of spontaneous brain activity.”

So what does this say about free will? “If we are correct, then the Libet experiment does not count as evidence against the possibility of conscious will,” says Schurger.

Cognitive neuroscientist Anil Seth of the University of Sussex in Brighton, UK, is impressed by the work, but also circumspect about what it says about free will. “It’s a more satisfying mechanistic explanation of the readiness potential. But it doesn’t bounce conscious free will suddenly back into the picture,” he says. “Showing that one aspect of the Libet experiment can be open to interpretation does not mean that all arguments against conscious free will need to be ejected.”

According to Seth, when the volunteers in Libet’s experiment said they felt an urge to act, that urge is an experience, similar to an experience of smell or taste. The new model is “opening the door towards a richer understanding of the neural basis of the conscious experience of volition”, he says.”

This does not prove that we have free will it only serves to show that the initial interpretation that we don’t have it (or that free will is an illusion) as Libet and more recently Sam Harris have claimed is not supported by the science.

Journal reference: Proceedings of the National Academy of Sciences, DOI: 10.1073.pnas.1210467109

It appears Libet never went so far as to deny free will based on his findings from what this article states.

“Although Libet himself stopped short of endorsing free will
scepticism on the basis of his results, other theorists have not been so cautious, and his work is often said to show that we lack free will.”

Jay, in the initial study he didn’t deny it, you’re right. But, in subsequent studies and in interviews after the study he SUGGESTED that free will was an illusion BECAUSE of his studies. Further, Sam Harris DID suggest that it was an illusion because of Libet’s work, he was wrong, just like I said he was (thanks to Al Mele’s work)!

Well, it’s important to keep in mind that this new study does not prove the existence of free will, not even close. It does, however, aim to debunk those that have claimed that free will is an illusion on the basis of the Libet experiments and subsequent experiences by Daniel Wegner.

I enjoyed your site. I like the way you analyze the research, draw conclusions and give a take home message. I also teach a brain fitness class for older adults, using the PositScience program, while offering information on brain health. I have bookmarked your site, and hope to hear more. I’ve learned a lot already!

Neither free will is proven nor Libet experiment against free is debunked.

“Showing that one aspect of the Libet experiment can be open to interpretation does not mean that all arguments against conscious free will need to be ejected.”

I can understand the importance for a student of Ethics, Metaphysics, and Epistemology, specifically; Free Will and Moral Responsibility, Moral Evaluations, Practical Reasoning, Environmental Philosophy, Animal Ethics, Consciousness, Moral Obligation, and Belief Justification to debunk any anti free will thesis or experiment.

But sorry to say it is not only Libet experiment that throws away free will, it is physics too. Believe me, much to my despair. The idea of me just being an automaton is disappointing, but seems to be right.

For more anti free will ideas see Who’s in Charge? by Michael Gazzaniga. He makes very convincing arguments against free will, although his justification for morality after the fact that there is no free will is ludicrous.

You’re right when you say “neither free will is proven nor Libet experiment against free (will) is debunked”. Luckily I have claimed neither. What I did claim, however, was that Libet’s particular interpretation of his experiment was debunked. I stand by that.

You claim that physics debunks free will? I’d love to hear that argument.

With regards to your comment on Gazzinga’s work; I read that book last year and did not see his arguments as an attack against free will. Many of those who have reviewed the book seem to agree with my interpretation. For instance, Y.S Fing from the Washington Independent Review of books says:

“Socialization, the reaction of the brain to other human action, puts an emergent mind in operation with other emergent minds. Because that action can’t be predicted, the brain is not hard-wired for specificity, but for flexibility and adaptability in its responses. As Gazzaniga puts it, “The social group constrains individual behavior, and individual behavior shapes the type of social group that evolves.” So the human mind is constrained in two ways, both by the structure and function of the brain itself and by the structures and functions of complex society. Gazzaniga says that humans are moral, responsible and have free will because their emergent minds exist in relation to each other. One example he gives is of criminals who “inhibit their intentions when [a] cop walks by.” His purpose is to declare, despite his peers’ conclusions, that people may be held accountable for their behavior. If their behavior is not exactly “conscious volition,” it certainly is not entirely determined by conditions.”

I hadn’t heard of or read anything about this follow up study challenging Libet’s work. Very glad I have found your blog! You just saved me from writing a very long post concerning the neuroscience of free will that I would have regretted! Great stuff. Looking forward to more.

The experiment begs the question that free will resides in our consciousness. Then it tries to disprove free will exists by demonstrating free will actually does exist at the subconscious level. Silly.

I’ve read millions of arguments, nah that’s just an exaggeration, but I have read enough for me to come to my own conclusions. Which is that we should keep our minds open to the possibilities and that our knowledge is still incomplete. It’s better than having a narrow minded view about the world like most proponents of the ‘Free Will is an Illusion’ camp seem to have. Rushing to conclusions helps no one.

Especially not when it comes to free will. The implications are profound and the more this false belief that free will doesn’t exist is propogated, I’m only calling it false now because it hasn’t been proven that it doesn’t,the more our social structures will collapse and that’s not a scenario I want to see. We might be animals but all animals are social . If dogs and cats can get along just fine , then why can’t we when we belong to the same species? When we have the skills necessary to build things , domesticate animals, come up with theories that try to define our world then we can definitely put in the extra effort to be kind to each other. It’s the least we can do .